This invention is concerned with semiconducting photodiodes.
The availability of optical fibers with low attenuation and minimum dispersion in the 1.3 to 1.6 .mu.m region has motivated research directed at the development of optical sources and photodetectors which will operate at these wavelengths so that practical fiber optical systems can be implemented in this region of the optical spectrum. The problems encountered in fabricating these devices, such as long wavelength avalanche photodiodes (APDs), have been primarily related to materials. The devices utilized in the prior art, which have been produced from germanium or Group III-V alloys, have exhibited a combination of high leakage currents, soft breakdowns, and relatively low gain. The high leakage currents of these detectors degrade the signal-to-noise performance and restrict the usable gain to low values.
Consequently, it has become desirable to identify a new photodiode technology which can provide acceptable performance in the longer wavelength region at which high performance optical fibers operate.